Sped up git-annex init in a clone of an existing repository

Seems that hasOrigin was never finding origin's git-annex branch, so a new
one got created each time. And so then it later needed to merge the two
branches, which is expensive.

Added --no-track to git branch to avoid it displaying a message about
setting up tracking branches. Of course there's no reason to make the
git-annex branch a tracking branch since git-annex auto-merges it.

Annex/Branch.hs

@@ -89,7 +89,7 @@ fullname = Git.Ref $ "refs/heads/" <> fromRef' name
 
 {- Branch's name in origin. -}
 originname :: Git.Ref
-originname = Git.Ref $ "origin/" <> fromRef' name
+originname = Git.Ref $ "refs/remotes/origin/" <> fromRef' name
 
 {- Does origin/git-annex exist? -}
 hasOrigin :: Annex Bool
@@ -114,7 +114,11 @@ getBranch = maybe (hasOrigin >>= go >>= use) return =<< branchsha
   where
 	go True = do
 		inRepo $ Git.Command.run
-			[Param "branch", Param $ fromRef name, Param $ fromRef originname]
+			[ Param "branch"
+			, Param "--no-track"
+			, Param $ fromRef name
+			, Param $ fromRef originname
+			]
 		fromMaybe (error $ "failed to create " ++ fromRef name)
 			<$> branchsha
 	go False = withIndex' True $ do

CHANGELOG

@@ -23,6 +23,7 @@ git-annex (8.20210311) UNRELEASED; urgency=medium
     operating on keys.
   * New annex.supportunlocked config that can be set to false to avoid
     some expensive things needed to support unlocked files.
+  * Sped up git-annex init in a clone of an existing repository.
 
  -- Joey Hess <id@joeyh.name>  Fri, 12 Mar 2021 12:06:37 -0400
 

Git/Ref.hs

@@ -84,7 +84,8 @@ dateRef r (RefDate d) = Ref $ fromRef' r <> "@" <> encodeBS' d
 fileFromRef :: Ref -> RawFilePath -> Ref
 fileFromRef r f = let (Ref fr) = fileRef f in Ref (fromRef' r <> fr)
 
-{- Checks if a ref exists. -}
+{- Checks if a ref exists. Note that it must be fully qualified,
+ - eg refs/heads/master rather than master. -}
 exists :: Ref -> Repo -> IO Bool
 exists ref = runBool
 	[ Param "show-ref"

doc/todo/Avoid_lengthy___34__Scanning_for_unlocked_files_...__34__/comment_6_e2718b6492d5da64a8bd6b13ad1cfa45._comment

@@ -0,0 +1,10 @@
+[[!comment format=mdwn
+ username="joey"
+ subject="""comment 6"""
+ date="2021-03-23T19:15:23Z"
+ content="""
+Found a way to speed up git-annex init's setup of the git-annex branch when
+run in a clone of an existing repo. In a 100,000 file repo, it improved
+from 17s to 10s. I have a feeling that might have been what was really
+making it seem slow to you.
+"""]]